Machine for grinding curved trimming blades



A. B. FOWLER. 1 MACHINE FOR GRINDING CURVED TRIMMING BLADES.

, APPLICATION HLED AUGJZ, l9l9- L42%196..

Patented Aug. 1,1922. zsmzers-snzsr 1.

A. B. FOWLER. MACHINE FOR GRINDING CURVED TRIMMII IG BLADES.

APPLICATION FILED AUG.22, I919- Patented Aug. 11 11922.

2 SHEETS-SHEET 2.

human retire raga? ALFRED Browne R, or nvi -n n a, nassncnusn'r'rs, ASSIGZNOR T0 UNITED sHon new autism.

uecnmn non eniguniue cunv nn maintainer BLADES.

specification of Letters Patent.

Patented Aug.

Applicationfiled eugust 22, 1919. Serial No. 319,181.

To all whom it may cm oern:

Be it known that 1, A FnnmB. Fow nn a citizen of the United States, residing at, Beverly, .in the county of Essex and State of .Massachusetts, .haye inyented vcertain Improveinents in Machines for Grinding Curved Trimming Blades, of .,whichv the following description, in ,connectionwith, the accompanying drawings, is, a specification, like reference characters, on; the drawings indicating like parts. in. the ,several figures.

This invention relates to ,machines for.

grinding cuttingblades. The invention is illustratedas embodied in a ln ach ne especiall desi nedfor, rindin thecom nanion' y a a a: .v

knives of a rotary cutter head.

For example, a well-knowntype ofheel trimming machine. employs a rotary ,cutter head having two diametrically mounted knives or bladeswhicharecurvedboth laterally and longitudinally as. shown, for Min stance, in Letters l iatent No. 5 1133 19 to Noble. Blades of this typeQ are curved rear wardly from their cutting edges, and are irregularly shaped transversely accord ng to the shape of that portion of the heel which is to be trimmed. A. blade of such shape is difiicult togrind-properly for the reason that its transverse, form interferesmvith accurate grinding to present a uniform cutting edge which must, for obvious lreasons, ,be parallel with the outside surface of theblade.

An important obj ectof the invention is to,

provide a machine capable of accurately grinding a blade of, the type referred to so i that theentire cutting edge will be inthe outside surface of the blade throughout the width thereof; without having the uniform- H ity of said cutting edge interferedwith by the curvature of said surface;

In the illustrated construction, the blade. to be sharpened is secured in a holder which i is traversed across the periphery of a grind:

ing wheel to present all points in the. entire edge of the blade to the wheel and, tomaintain the proper bevel, on the edge of the blade, the blade is given a feedingmovement by the holder in a curvedpath corresponding to the curvature of the bladerearwardly from its cutting edge. As shown, the parts.

are soorganized that thebladecan-also be rocked (hiring its traversing movement to impart a predeterm ned shapeto the cutting edge and tl e feeding of the blade in a curved path is'accomplishedstep step under the controlpt the;traversing.movement i To enable each of t wo companion blades ef;. -wtte t eee 9f sas ty e-a filli stralt d in the patent above mentioned to: do its share of trimming ork properly, I it is essential'lthat the, cutting, edges of the blades shall be ex actly, alike. It is obvious that even an 1 ex- [pert who, able to, grind one such blade with accuracy. by a me1 e 1 of the relat ve moyeinents of the blade and grinder cannot take the companion blade and grind t xeetlul ke fir t A A te pt have been made to produce or sharpenthe' compan on, blades oi lthe kind referred to so that they shall accurately correspond bytheemployment of te nplet devices which control they 'movements ot a blade past 'a grinder and toward andfromflit'but so. far as Iain aware, i such .niachi nes either, necessitate operation flrst on one bladeand thenitsremoval and substitution oflthe companion blade there- ,for, or else employ, two teinplets forthe t wo blades. In the firs tease, there is no cerprises a'grinding wheel and a carriage, one

, of, which is movable pastand toward and from'the other, a lwork holder, mounted on the carriage for securing a plurality of blades in edge-to-edge relationship, means to feed the work holder along the carriage top ward the grinding wheel, and. a controlling means such as a teinplet mechanism for controlling, the shape to be imparted 'by, the grinder tothe edges ofaplurality, of blades.

Another. feature of the inventionfconi ists in a novel grinding machineh'aving a plurality of rotatably mounted templets for controlling'the path. of l movementpof a blade and wheel relativelytofeach other,

means being provided whereby either one of thete nplets can be rigidly secured in operaivpb t i These and other features of the invention including certain details of construction and combinations of, parts will now be described in connection with the accompanying draw-,

ings. vof an illustrative embodiment of the invention. 3

Of the drawings, 1 r 1 Fig. 1 is a front elevation of the machine,

the manually operable handle being shown -in section;

v Fig. 2 is'an elevation looking from the right of Fig.1 Q I Fig. 3"repres'ents a section-online Fig-1, on a larger scale.

Fig.4 is a perspective view of parts of the machine, partly broken out, looking from the upper right hand corner of Fig; 1;

Fig. 5 is a broken out perspective view,

looking, from below, of the'work carriage,

'j parts being omitted in the interest of clearness;

' Figzj6 is a ratchet control. mechanism; and Fig. 7 represents a' section on Figure 6.

' detail elevation of a pawl and line 7 7 of The upper portion of asnitable frame or' standard l2'carries a trough 13 above which is'ni'ounted a grinding wheel l4lcarried by a i carefully and accurately to adjust thegrindjshaft 15. Said shaft, bestshown in Fig. '1, i's mounted in a'bearing housing 16 car- *-ri'ed by a post 17 mounted in clamp 18 35 illustrated as" supported atone end ofthe trough 13. *As' it is "sometimes desirable ing wheel to compensate for reduction of the diameter of the wheel due to wear, I"provi'de a screw 19 threaded inn lug 20 at one side of the clamp 18 so that, whenthe clamp 18 is loosened. verticaladjustinent of the shaft: housing 16' may be effected by'nieans the screw a r Which the clamp .18 is again tightened.

A suitable hood for the grinding wheel is indicatedat 21, and said hood may be of any well-known or preferred construction.

Rising fronrthe rear of that-rough 13 is a frame 'bracket 22 having arms 23 which a're'spaced as best shown in'Fig. 1 and support a fixed rod'24. which forms a slideway or guide for the'work carriage. Mounted on the rod24l is a carriageslide 25 having pinfEZGentering a slot in a hand lever 27 pivoted at 28 to a stud of the bracket 22. The carriage slide 25 has forwardly cxtend ng arms 30 integrally 'or otherw se connected with a curved plate 31 which, at each flanges 32' to form ways for the similarly curvedwork-carrying plate 33. The plate '33 has aninte'gral'or otherwise fixed central end, is formed or provided with grooved stud '3t'and near each end thereof has'bearing faces 35 for the inner ends of blocks or clamp members 36. A rod 37 passes through ,a bearing 38 projectingfroin one end of the plate 33 and also through bothblocks 36 and the central stud" 34, said rod having threaded. engagement with one of the blocks 36 and having a collar 39 outside of the other block 36 so that, when the rod 37 is rotated in the proper direction, the space between the blocks 36 will be contracted. The blocks 36 and the central stud 34 are formed with grooves 40 to engage op ositeedges of two blades a-0; (Fig. 4)." ne end of the rod 371s provided with a head or handle 41 by means of'which said rod can be rotated to draw the blocks 36 toward the'central member 34: so as to clamp the two blades a, one between one of the blocks 36 and one side of said central stud 34- and the other between theother side of said stud 34 and the other block 36. The rod 37 is free to have sufficient longitudinal movement in the bearings 38 to result in clamping the blades in the manner described, the two blades being held firmly against the central stud 34 which is fixeds'o far as anylateral movement might be considered and therefore definitely loriage during its endwise movements rela tively to tlieigrinding'wheel will result in "imparting a certain "contour to the work supported by the carriage, when the said work is in proper-proximity to the grinding wheel' I will now describe the temples mechanism which effects this control. Prothe carriage 25 are two arms 42 carrying a pin or shaft 13. Mounted on the pin or shaft l3 is a hub or sleeve 44 having a plurality of radial flanges 45 having shoulders against'which the inner edges of templets 46 bear or rest, said templets being secured to the flaiiges'by suitable bolts 47. This structure of teinplet carrier renders it possibleto easily employ. different shapes of tem-' ,plets, substituting one for another whenever desired] The'outer edge of any one of theteinp-lets 46 acts'to control the work by 'co-operating with aroll 48 'mounted on a pin 4-9 carried by a bar 50 extending transversely between. the arms 23 of the frame bracket '22. j'As will be readily understood from Fig. 2. the weight ofthe parts is such thatthere is anornial tendency of the work carriage andqt'he arms- 42 thereof to swing toward the right from the position shown in said figure so that, as the'carriage is shifted 'along the rod24; by the operators manipulation of thehandle 27, the entire carriage will be rocked to swing the work relatively jectingrearwardly and downwardly from to the axis of the grinding wheel due to the bearing of the edge of a templet 46 against the roll The guide surface of each term plet is made suliiciently long to extend across the cutting edges of both blades so that one complete traverse of the carriage results in the shaping of two blades.

Suitable means are provided for holding the selected templet inv position. the means illustrated comprising a detent 51 (Fig. 4) pivoted at 52 to an enlargement 01. one of the arms l2 and having a linger piece 555, said detent having a spring stud 5e bearing against the bottom of the recess in which the detent is mounted so as to have a normal tendency to hold the detent 51 in the position best shown in Fig. 1. Whenever it is desired to bring a new radially mounted templet into position to co-operate with roll t8, the operator presses against the finger piece 53 to swing the detent 51 outwardly so as to release the templet with which the yoke-shaped end of the detent was engaged, after which the hub or sleeve er is F rotated to bring the desired templet into position to 00-2101; with roll 48 and then the detent is released to engage the said templet the end of which has been brought opposite said detent by rotative adjustment oi? the sleeve. lie-engagement ot the yoke-shaped end of the detent with a templet locks the entire series.

As best shown in Fig. at the body of the carriage comprises the slide 25, the curved plate 31 and the arms d2. A. rod or shaft 55 having a. key-way 56 and a handle 57 is mounted in suitable hearings in the carriage so that it can be rocked. The handle 57 has a cam 58 the purpose of which will be presently described.

Mounted on the rod are two fingers 59 having hook-shaped ends, the hubs of said fingers having suitable keys such as screws 60 the inner ends of which engage the keyway 56. Projecting from the hubs of the fingers are tongues 61 entering recesses 62 in'the work clamp members 36 (Figs. 1 and 5), the engagement of said tongues and recesses ensuring that whenever the clamp members 36 are shifted relatively to the central stud 3 1:, the fingers 59 will correspondingly move so as to always be in position to engage predetermined lateral portions ot' the rear edges of the blades a, a as will be hereinafter described.

Secured to the rock shaft 55 adjacent a bearing portion which projects from the central stud 3 1 is a cam 63 to act upon the arm or tail piece 64 of: a finger 65 the hub of which is rotatably mounted on the rod- 37. A suitably connected spring 66 causes the finger 65 to rise when permitted to do so by the cam 63.

A portion of one of the bearings 38 is extended, as best-shown in Fig. 5, and has an upwardly projecting web the upper surface of which is toothed to form a somewhat segmental rack 67, the curvature of the rack teeth 67 corresponding with the radius .of curvature of the ways 32 and clamp carrying plate Engaging the rack 67 is a worm 68 mounted in bearings 59 (Figs. 2'and 4;) which may be ii'itegral with the curved plate 31. A spring 70 has one end connected to a collar at the end of the worm, said spring having its other end connected to the plate 31, the action of this spring being, as hereinafter explained, to return the worm (38 to normal position after said worm has been rotated to effect a feeding operation which will be explained. Secured to the other end or the worm 68 a ratchet 71 (Figs. 3, 4-, 6 and 7) and hung upon a reduced end portion of the worm, close to the ratchet 71 is an arm 72 carrying a ratchet actuating pawl 7 3. A stop pin 74 limits the movement of the arm 72 in one direction.

and a spring 75 is connected to said stop pin and to the arm 72 to normally hold the latter in the position. shown in Fig. 6.

When the carriage is shifted toward the right in Fig. 1. by means of the hand lever 27, the arm 72 contacts with the inner end of a screw 76 carried by a fixed arm 77 secured to one end of the rod or slideway 24, the contact of the arm 72 with said pin 76 causing the pawl 7 3 to impart a step of rotation to the ratchet 71 and the worm 68. A detent pawl 78 is pivotally supported by the lower portion of bearing bracket 69 and has a pin 79 extending over the cam 58. The outer end of pin 79 extends across the heel of the actuating pawl 73 (Figs. 3, 4 and 6). Suitable sprin s are provided to hold. the pawls 73 and 48 in position to cause their tips to engage the ratchet so that pawl 73 may actuate the ratchet and the pawl 78 prevent return movement. 1

In operation, assuming that no blades are in place to be ground. and that the handle 57 is in the position shown in Fig. Ehthe fingers 59. 65 will be in the positions shown in that figure. This is because the rock rod 55 swings the fingers 59rearwardly and the cam 63 occupies such position that the spring 66 (Fig. 4) holds the front finger {55 raised. At this time it is also to he assumed that the rod 37 has been actuated to provide tor such spreading apart of the two clamp members 36 as to leave space between the said. members 36 and. the central member 34; to permit of the introduction ottwo blades a, a into the grooves 40. Before the bladesare clamped. edgewise by contraction of the members 36 toward each other. the rock rod 55 is actuated by its handle 57 in the direction of the arrow 1' in Fig. 3, and this results in swinging the fingers 59, 65, toward theposition indicated in Fig. 2. The result of this movement is thatthe one finger 65 shown in Fig. 4 movesto position in time so that its hooked tip will serve as a stop to limit the forward position to which the blade 46 can be shifted or pushed by the finger 59 which is shown at the left in Fig. at. This determines the proper forward position to be occupied by blade 0; at the beginning of the grinding operation. The reason why there is no front stopping or limiting linger for the other blade a is that since the two lingers 59 are carried. by the one rock rod 55, said two fingers 59 will act to push both blades forward in the guides 40 so as to locate their rear edges in the same plane. Consequently if the two bl-adeso, a are of the same length from front to rear the front or cutting edges of both will be determined by the one forward finger 65. If the blade at in Fig.4 islonger than blade a. its front edge will, of course,projectnearer the grinding wheel than the front edge of blade at, and then grinding action will be had only upon the front edge of blade at until its length from front to rear has been reduced to the same length as blade (6. On the other hand, if blade at is shorter than blade a, grinding will be'eifected only on blade 0 until its length is reduced to that of blade at. The

final result will be the production .of two.

-thenrise to normal position where they will not interfere with further operations. Then the clamp rod 37 is actuated to cause,- the ,clamp members 36 to approach-the central member 34, whereby the blades will. be held firmly in edgewise relationship ready for the grinding operation. V

The operator, by means of the handle 27, shifts the carriage back and forth along the slideway 24, the edges of the two blades being carried past and in contact with the periphery of the grinding wheel, the carriage oscillating or swinging as it is so traversed, the degree of the oscillations being controlled by the coaction of one of thetemplets 46 with the roll 48. 7

Each time that the operator traversesithe carriage toward the right in Fig. 1, he moves it until arrested by the arm 72 coming in contact with the screw 76 (Figs. 1 and 1).

This contact is sufficient to swing thearin 72 slightly but far enough to cause the pawl 72 to act on the ratchet 71 to impart a slight rotation to, the worm 68. Said worm, by

acting on the rack 67 of the bearing 38,v

outside surfaces thereof.

further. operation of the wheel upon the front edges of the blades. Usually there will be several traverses of the carriage before grinding is completed, and for every such traverse there is aslight forward feed or advance of the blades toward the grinding wheel in a curved path corresponding to the curve of the blades. Consequently the bevel of the front edges of the blades will not be altered by the gradual feed and the cutting edges of both blades will always be in the Each step rotation of theworm 68 acts to slightly wind upthe spring 70. 1

When grinding has proceeded far enough, the operator swingsthe handle 57 downward to the position shown in Figs. 2 and at, far enough to cause the cam 58 to engage pin 79 and lift. it. As said pin is mounted in the detent pawl78 and extends past the actuating pawl 73, the lifting of saidpin 79 disengages both of the pawls from the ratchet which immediately then rotates backwardly under the influence of the power which hasbeenstored in spring 70. The consequent rotation of worm 68 acts, through rack 67, to return the curved feed plate 33 to normal position, after which the ground blades are removed and new ones may be inserted and the operation repeated as described. g

While the invention has been especially designed with reference to the production of two blades ground exactly alike, I do. not limit myself to such use of the machine. Sometimes it may be desired to grind but a singleglade. In such case only one blade will be fitted in the position of blade a in Fig. The operation will be the same as hereinbefore described except that the user will then, by means of the handle 27, traverse the carriage through only approximately it of the distance provided for on slideway 2%.

Having described my invention, what I claim'as new and desire to secure by Letters Patent of theUnited States is:

1. A machine for grinding trimming blades, having, in combination, a'grinding wheel, a carriage, a fixed guideway, means for causing movement of the carriage along the guideway to grind the entire edge of the blade, means to rock the carriage to. impart predetermined shape to the blade, and means for feeding the'bladeedgewise on the car riage toward the wheel. 7 12 p 2. A machine for grinding trimming blades, having, in combination, a grinding element, a slideway, a carriage mounted to slide and rock on said slideway, mechanism for controlling rocking movement of the carriage, and meansto feed theblade edgewise along the carriage toward the grinding element.

. 3. A machine for grinding trimming blades, having, in combination, a grinding td dalw wheel, a carriage movable past. the grinding wheel, means to rock the carriage in its movement past the wheel, and means responsive to the movement oi the carriage for feeding the work on said carriage toward the grinding wheel.

4L. n1achine for grinding curved trimming; blades having, in combination, a grinding wheel and a work carriage one of which is movable relatively to the other longitudinally ot'; the axis. ot the wheel, a blade holder mounted. in said carriage, means for feeding; the holder in a curved path corresponding to the curvature ofthe blade rearward ly from its cutting edge, and'means for varying the distance between the holder and wheel during traverse longitudinally of the axis ofthe wheel to. impart a predetermined shape to the blade.

5. A. machine for grinding curved trimming blades having, in combination, a grinding wheel and a work carriage one of-wwhich is movable relatively to the other longitudinally of the axisof the wheel, a blade holder mounted in said carriage, means for feeding the holder step by step ina curved. path corresponding; to the curvature of the blade rearwardly from its cutting edge, and means for, varying the distance between the holder and wheel. during traverse in. the direction of the axisof the wheeLsa-id distance varying mechanism including a templet and a coacting; abutment therefor one of which is connected. to the carriage.

6. A machine of the character described having, in, combination, a grinding wheel and a carriage oneof which is movable past and toward and from the other, a work holder mounted on the carriage for securing a plurality of blades in edge-to-edge relationship, means to feed the work holder along, the carriage toward the grinding wheel, and a single controlling mechanism for determining the shapeto be imparted by the wheel to the plurality of blades.

7,. In a machine of the character described,

a. grinding wheelyaguide rod parallel with the axis of said wheel, a carriage mounted to slide and rock on said guide rod, teinplet mechanism for controlling rocking movements of the carriage, means for feeding the work along the carriage toward the wheel, and a manually operable lever for shifting the carriage alongthe guide rod. 7 8. In a machine of the character described, a grinding wheel, a carriage mounted to move past the wheel, said carriage having curved ways, a plate mounted in said ways, a central stud carried by said. plate, blocks slidably mounted on opposite sides of said central stud,-the said. stud and blocks having grooves for engaging opposite edges of blades to be ground, and means for actuating the blocks toward the central stud; to clamp blades in said grooves.

clampcarrying plate in a direction toward the grinding wheel.

10. In a machine of the character described, a grinding wheel, a carriage mounted to move past the wheel, said carriage being constructed, and arranged to'oscillate relatively to the wheel, said carriage having curved ways, a work carrier mountedin said ways, means for automatically feeding the work carrier in the direction controlled by said ways, and templeumechanism for controlling oscillations of the" carriage;

11; A machine of. the character described raving, in combination, a grinding wheel and a work ho-lderone of which is movable past and toward and'l rom the other, a templet-carryin'g shaft and an abutment one of? which is connected with the work holder and the other with astationary part of the machine, a rotatable hub having a plurality of templets rigidly secured thereto, and means for securing said hub in different angular positions to present 'either" one of its templet's to the co-operating abutment.

12, A. machine of the character described having, in combination, ajgrindingwhed and a work holderone of which is movable past and toward and from the othena rotatably adjustable hub carried by the work holder and having a plurality of radially extending tcmplets rigidly secured thereto, and a stationary abutment to co-operate with eitherone of said templets. p

1 7 In a machine of the character described, a grinding wheel, a work carriage mounted to move past and toward and from the wheel, arot-ata blyv mounted hub having a plurality of templets and being carried by the carriage, means for securing" the hub rigidly .in different angular positions to bring any desired templet to working position, and an abutment for one of said templ t 14;, In a machine of the charaeterdescribed, a grinding. wheel, a worl; carriage mounted to move past and toward and from the wheel, a pair of armsegrtending from said carriage, a hub rotatably supported by said arms andhaving a plurality of radial ane'es, templets secured to said flanges, and an abutment for one of said templets.

15. In a machine of the character described, a grinding wheel, a work carriage ltd said armsand having a plurality of radial flanges, templets secured to said flanges, a

, detent for engaging one of the templets to lock. them in rotatably adjusted position and an abutment for one of the templets.

,16. In a machine of the character described, a grinding wheel, a fixed guide extendin past the wheel, a slide mounted I on saic guide and having ways ata right angle to the guide, means for rocking said r-slide on the fixed guide, a work clamp mounted in said ways, andj means for automatically; shifting-the work clamp in the ways towardthe grinding wheel. v j

; 1,7. In a machine of the character described,"a grinding wheel, a carriage mounted to slide ast the wheel, said carriage havinga pair of'clamps for holding two blades in edgewise alinement, and a rock rod mounted in the carriage and having two fingers for, engaging the rear edges of the blades to adjust them in the clamps.

18. In a machine of the character described, a grinding wheel, a carriage mounted to slide past the wheel, said carriage having a pair of clamps for holding two blades in edgewise alinement, a rock rod mounted in the carriage and having two fingers for engaging the rear edges of the blades to adjust them in the clamps, and a movable finger to engage the front edge of oneof the blades to limitthe forward positionof adjustment thereof. 7 l i 19. In :a machine ofthe character described, a grinding wheel, a carriagemounted to slide past the wheel, said carriage having a pair of clamps for holding two blades in ,edgewisealinem'ent, a rock rod mounted 1n the carriage and having a longitudinal key-wa a pair of fingers mounted on the rod an having portions engaging said'keyway, andlconnections between the fingers and clamps to shift the fingers along the red when the clamps are adjusted;

20. In a machine of the character described, a grinding wheel, a carriage mounted, to slide past the wheel, said carriage. having a pair of clamps for holding two blades n.edgewiseIalinement, a rock rod mounted infthecarriage and having a longitudinal key-way, a pair of fingers mounted on the rod and having portions engaging said keyway,.'and connections between the fingers and clamps to shift the fingers alon the rod when theclamps are adjusted, sai connections comprising tongues carried by the fin clamps.

gers f and ,tongue receiving recesses in the name to this specification.

'21. In 'amaohine of the character described, a grinding wheel, a carriage mounted to slide past the wheel, said carriage having a pair of clamps for holding two blades in edgewise alinement, a rock rod mounted in the carriage and having a cam, fingers carried by said rod for engaging the rear edges of the blades to adjust them in the clamps, and a pivotally mounted finger to limit the forward adjusted position of one of the blades, said finger having an arm bearin on the cam of the rock rod.

22. n a machine of the character described, a grindingwheel, a carriage mounted to move past the Wheel, said carriage having curved ways, a work carrier mounted in said ways and means'for automatically feeding the work carrier in 'thedirection controlled by said ways, said feeding means comprising a toothed segment carried by the work carrier, a wormengaging said segment, and means for actuating the worm when the carriage is shifted.

23. In a machine of the character described, a grinding wheel, a curved plate mounted to slide pastthe wheel and having its ends provided with transverse ways, a clam gcarrying'plate mounted in said ways and" iaving a toothed segment, a worm carried by the slide plate and engaging the segment, and means for imparting intermittent rotations to the worm to feed the clamp carryingiplate toward thegrinding wheel,

24. In amachine ofthe' character described, a grinding wheel, acurved plate mounted to slide past the wheel and having its'ends provided with transverse ways, a clamp carrying plate mounted in said ways and having a toothed segmen't,' a worm carried by theslide plate and e'ngaging the segment, a ratchet carried by the worm, an arm having a pawl engaging the ratchet, and an abutment inthe path of movement of said arm to effect-a slight rotation of the worm to feedthe clamp carrying plate each time the arm contacts withsaid abutment.

25.7 In a machineof the character described, agrinding wheel, a carriage having work clamps mounted to slide past the wheel, means for automatically feeding the work clamps transversely of the carriage toward the wheel, a rock rod having a handle and a cam and work engaging fingers, and meansengaged by the cam 'ofthe rock rod to render' the feeding means inoperative when the said fingers: are engaged with the work; 4 s, In testimony whereof I have signed I 

